The present invention relates to a manufacturing method of a semiconductor device having a memory element such as MTJ (Magnetic Tunnel Junction) element.
MRAM is a memory using a magnetic material as a memory element and storing data, depending on the magnetization direction of the magnetic material. In other words, it is a memory storing data in the spin of electrons, thereby holding the data and it has a randomly accessible circuit. The memory element to be utilized as MRAM is, for example, an MTJ element. The term “MTJ element” in this specification is used as a concept including a TMR (Tunneling Magneto Resistance) element.
A method of forming a silicon nitride film (plasma SiN film) as a protective film for covering a memory element of MRAM therewith has conventionally been employed. It is the common practice to form this silicon nitride film by a CVD method with an ammonia gas (NH3), a silane gas (SiH4), and a nitrogen gas (N2) as a film forming gas. Such a silicon nitride film formation method is disclosed in Japanese Unexamined Patent Publication No. 2007-305645.